JP6878975B2 - Batteries - Google Patents

Description

The present invention relates to an assembled battery including a plurality of square secondary batteries.

As a power source for driving an electric vehicle (EV), a hybrid electric vehicle (HEV, PHEV), or the like, an assembled battery in which a plurality of square secondary batteries are connected in series or in parallel is used.

In such an assembled battery, a plurality of square secondary batteries are arranged so that the wide side surfaces of adjacent square secondary batteries face each other with a spacer or the like. For example, a plurality of square secondary batteries are arranged between a pair of end plates, and the pair of end plates are connected to each other by a bind bar to form a single assembled battery (Patent Document 1 below).

As a square secondary battery, a flat wound electrode body in which a long positive electrode plate and a long negative electrode plate are wound via a long separator is housed in a square battery case. It has been known. In such a square secondary battery, the wound electrode body expands due to charging / discharging or the like. Further, as the charge / discharge cycle progresses, the expansion of the wound electrode body increases. Then, such expansion of the wound electrode body is remarkable in a square secondary battery having a high volumetric energy density. When the wound electrode body expands, the wound electrode body pushes the battery case outward, and the square secondary battery expands. If the square secondary battery expands and the force (reaction force) that presses the other is excessively large, the members constituting the assembled battery, such as the bind bar and the end plate, may be damaged or damaged. In addition, the expansion of the square secondary battery may reduce the battery performance of the square secondary battery.

JP-A-2015-210971

One object of the present invention is to prevent the assembled battery from being damaged or damaged due to the expansion of the square secondary battery.

The uniform assembled battery of the present invention is an assembled battery in which a plurality of square secondary batteries are arranged via spacers, and the square secondary battery is a long positive electrode having a positive electrode active material mixture layer. A flat wound electrode body in which a plate and a long negative electrode plate having a negative electrode active material mixture layer are wound via a long separator, an opening, a bottom, a pair of first side walls, and It has a pair of second side walls, and includes a square exterior body for accommodating the wound electrode body, and a sealing plate for sealing the opening. The area of the first side wall is larger than the area of the second side wall. The wound electrode body includes a wound positive electrode core body exposed portion arranged on one side of the pair of second side walls and a wound negative electrode core arranged on the other side of the pair of second side walls. It has a body exposed part. A positive electrode current collector is joined to the exposed positive electrode core to form a positive electrode joint, and a negative electrode current collector is joined to the exposed negative electrode core to form a negative electrode joint. The wound electrode body has a power generation unit in which the positive electrode active material mixture layer and the negative electrode active material mixture layer are laminated via the separator. The power generation unit has a flat portion having a flat outer surface, a first curved portion having a curved outer surface and located closer to the sealing plate than the flat portion, and a curved outer surface, which is more than the flat portion. It has a second curved portion located on the bottom side. The boundary between the flat portion and the first curved portion is defined as the first boundary portion, and the boundary between the flat portion and the second curved portion is defined as the second boundary portion. In a direction perpendicular to the bottom portion, the end portion of the positive electrode joint portion on the sealing plate side and the first portion.
Let L1 be the distance from the boundary. In the direction perpendicular to the bottom portion, a region of 0.25 × L1 to 0.75 × L1 is formed from the end portion of the positive electrode joint portion on the sealing plate side of the power generation portion toward the first boundary portion. Let it be the first area. Let L2 be the distance between the end of the negative electrode joint on the sealing plate side and the first boundary in the direction perpendicular to the bottom. In the direction perpendicular to the bottom portion, a region of 0.25 × L2 to 0.75 × L2 is formed from the end portion of the negative electrode joint portion on the sealing plate side of the power generation portion toward the first boundary portion. This is the second area. Let L3 be the distance between the bottom-side end of the positive electrode joint and the second boundary in the direction perpendicular to the bottom. In the direction perpendicular to the bottom portion, a region of 0.25 × L3 to 0.75 × L3 is formed from the bottom end side of the positive electrode joint portion of the power generation portion toward the second boundary portion. There are 3 areas. Let L4 be the distance between the bottom-side end of the negative electrode joint and the second boundary in the direction perpendicular to the bottom. In the direction perpendicular to the bottom portion, a region of 0.25 × L4 to 0.75 × L4 is formed from the bottom end side of the negative electrode joint portion of the power generation portion toward the second boundary portion. There are 4 areas. Of the regions that overlap with at least one of the first region and the second region in one of the pair of first sidewalls when viewed from a direction perpendicular to one of the pair of first sidewalls. The area of the region pressed by the spacer is 20% or less of the area of one of the pair of first side walls that overlaps at least one of the first region and the second region. Of the regions that overlap with at least one of the third region and the fourth region in one of the pair of first side walls when viewed from a direction perpendicular to one of the pair of first side walls. The area of the region pressed by the spacer is 20% or less of the area of one of the pair of first side walls that overlaps at least one of the third region and the fourth region.

The inventor has set the joint portion between the positive electrode core body exposed portion and the positive electrode current collector and the joint portion between the negative electrode core body exposed portion and the negative electrode current collector as a reference in a square secondary battery provided with a flat wound electrode body. , It was found that a specific region of the flat wound electrode body easily expands due to charging / discharging or the like. Then, based on this finding, a specific region of the flat wound electrode body is set based on the joint portion between the positive electrode core body exposed portion and the positive electrode current collector and the joint portion between the negative electrode core body exposed portion and the negative electrode current collector. It has been found that the reaction force can be reduced and the excessive load applied to the frame such as the end plate and the binder bar constituting the assembled battery can be suppressed by preventing the pressure from being pressed.

Further, in the above-mentioned one type of assembled battery, in the flat wound electrode body, a portion that is particularly easily expanded by charging / discharging or the like can be configured so as not to be pressed by the spacer. Therefore, even if the flat wound electrode body expands due to charging / discharging or the like, an increase in reaction force can be suppressed, and an excessive load is suppressed from being applied to a frame such as an end plate or a binder bar constituting the assembled battery. it can. Therefore, it becomes a more reliable assembled battery.

If at least one of the pair of wide side walls of the square secondary battery, that is, the pair of first side walls, is provided with a region that is not pressed by the spacer, the reaction force in the region that is not pressed is provided. The increase is suppressed. Therefore, the increase in the reaction force can be suppressed by setting the pressing state by the spacer to a specific state in at least one of the pair of first side walls of the square secondary battery.

Of the regions that overlap with at least one of the first region and the second region in the other of the pair of first sidewalls when viewed from a direction perpendicular to the other of the pair of first sidewalls. The area of the region pressed by the spacer is preferably 20% or less of the area of the region overlapping at least one of the first region and the second region on the other side of the pair of first side walls. Further, when viewed from a direction perpendicular to the other of the pair of first side walls, the other of the pair of first side walls overlaps with at least one of the third region and the fourth region. Of these, the area of the region pressed by the spacer is preferably 20% or less of the area of the region that overlaps at least one of the third region and the fourth region on the other side of the pair of first side walls. ..

By setting a specific region not being pressed by the spacer on both of the pair of first side walls of the square secondary battery, the increase in reaction force can be suppressed more effectively.

When viewed from a direction perpendicular to one of the pair of first side walls, one of the pair of first side walls overlaps the flat portion and is between the first region and the third region. It is preferable that the region overlapping the located region is pressed by the spacer.
When viewed from a direction perpendicular to the other of the pair of first side walls, the other of the pair of first side walls overlaps the flat portion and is between the first region and the third region. It is preferable that the region overlapping the located region is pressed by the spacer.

In the pair of first side walls of the square secondary battery, it is preferable that the region facing the power generation portion of the wound electrode body and which is difficult to expand is pressed by the spacer. With such a configuration, even if a strong impact or vibration is applied to the assembled battery, it is possible to reliably prevent the wound electrode body from moving inside the square exterior body.

When viewed from a direction perpendicular to one of the pair of first side walls, one of the pair of first side walls overlaps with the flat portion and the first region, the second region, and the first side wall. Of the three regions and the region that does not overlap with the fourth region, the area of the region pressed by the spacer overlaps with the flat portion in one of the pair of first side walls and the first region and the second. It is preferably 70% or more of the area of the region, the third region and the region that does not overlap with the fourth region.

It is preferable that at least one of the pair of first side walls of the square secondary battery faces the power generation portion of the wound electrode body and presses a region that is difficult to expand with a spacer. With such a configuration, even if a strong impact or vibration is applied to the assembled battery, it is possible to reliably prevent the wound electrode body from moving inside the square exterior body.

When viewed from a direction perpendicular to the other of the pair of first side walls, the other of the pair of first side walls overlaps with the flat portion and the first region, the second region, and the first side wall. Of the three regions and the region that does not overlap with the fourth region, the area of the region pressed by the spacer overlaps with the flat portion at the other of the pair of first side walls and the first region and the second. It is preferably 70% or more of the area of the region, the third region and the region that does not overlap with the fourth region.

In both of the pair of first side walls of the square secondary battery, it is preferable that the region facing the power generation portion of the wound electrode body and which is difficult to expand is pressed by the spacer. With such a configuration, even if a strong impact or vibration is applied to the assembled battery, it is possible to more reliably prevent the wound electrode body from moving inside the square exterior body. The portion pressed by the spacer may be different in each of the pair of first side walls of the square secondary battery.

In the spacer, when viewed from a direction perpendicular to one of the pair of first side walls, one of the pair of first side walls overlaps at least one of the first region and the second region. It is preferable that the first recess is provided in the portion facing the region.
In the spacer, when viewed from a direction perpendicular to one of the pair of first side walls, one of the pair of first side walls overlaps with at least one of the third region and the fourth region. It is preferable that the second recess is provided in the portion facing the region.

In the spacer, it is preferable to provide a recess in a specific region of the surface facing the first side wall of the square secondary battery so that the specific region of the first side wall of the square secondary battery is not pressed by the spacer.

According to the present invention, it is possible to prevent the assembled battery from being damaged or damaged due to the expansion of the square secondary battery.

It is a perspective view of the square secondary battery which concerns on embodiment. FIG. 2A is a cross-sectional view of the IIA-IIA cross section in FIG. 1, and FIG. 2B is a cross-sectional view of the IIB-IIB cross section in FIG. It is a perspective view of the assembled battery which concerns on embodiment. It is a top view of the positive electrode plate. It is a top view of the negative electrode plate. It is a top view of the wound electrode body which concerns on embodiment. It is a perspective view of the spacer which concerns on embodiment. It is a figure explaining the structure of each sample. It is sectional drawing of the square secondary battery and the pressing jig in sample 1. FIG. It is sectional drawing of the square secondary battery and the pressing jig in sample 2. It is sectional drawing of the square secondary battery and the pressing jig in sample 3. It is sectional drawing of the square secondary battery and the pressing jig in sample 4. It is a top view of the wound electrode body which concerns on a modification. It is a top view of the wound electrode body which concerns on a modification. It is a perspective view of the spacer which concerns on a modification.

First, the square secondary battery 20 according to the embodiment will be described. FIG. 1 is a perspective view of the square secondary battery 20. FIG. 2A is a cross-sectional view of the IIA-IIA cross section in FIG. FIG. 2B is a cross-sectional view of the IIB-IIB cross section in FIG. The square secondary battery 20 has a battery case including a bottomed square tubular square exterior body 1 having an opening and a sealing plate 2 for sealing the opening of the square exterior body 1. The square exterior body 1 has a bottom portion 1a, a pair of first side walls 1b, and a pair of second side walls 1c. The pair of first side walls 1b are arranged so as to face each other. The pair of second side walls 1c are arranged so as to face each other. The area of the first side wall 1b is larger than the area of the second side wall 1c.

In the square exterior body 1, a flat wound electrode body 3 in which a long positive electrode plate 40 and a long negative electrode plate 50 are wound via a long separator is arranged. The winding electrode body 3 is arranged in the square exterior body 1 so that the winding axis thereof is parallel to the bottom portion 1a of the square exterior body 1. In the wound electrode body 3, a wound positive electrode core body exposed portion 4 is provided at one end in the direction in which the winding shaft extends, and a wound negative electrode core body exposed portion 5 is provided at the other end. Is provided. The wound electrode body 3 has a pair of flat outer surfaces and a pair of curved outer surfaces connecting the pair of flat outer surfaces. The pair of flat outer surfaces are arranged so as to face the first side wall 1b, respectively. Further, the wound positive electrode core body exposed portion 4 and the wound negative electrode core body exposed portion 5 are arranged so as to face the second side wall 1c, respectively. An electrically insulating resin sheet 14 is arranged between the square exterior body 1 and the wound electrode body 3.

A positive electrode current collector 6 is connected to the outer surface of the wound positive electrode core body exposed portion 4. A positive electrode terminal 7 is attached to the sealing plate 2. The positive electrode current collector 6 is electrically connected to the positive electrode terminal 7. An external insulating member 10 made of resin is arranged between the positive electrode terminal 7 and the sealing plate 2. A resin internal insulating member 11 is arranged between the positive electrode current collector 6 and the sealing plate 2.

A negative electrode current collector 8 is connected to the outer surface of the wound negative electrode core body exposed portion 5. A negative electrode terminal 9 is attached to the sealing plate 2. The negative electrode current collector 8 is electrically connected to the negative electrode terminal 9. An external insulating member 12 made of resin is arranged between the negative electrode terminal 9 and the sealing plate 2. A resin internal insulating member 13 is arranged between the negative electrode current collector 8 and the sealing plate 2.

In the wound positive electrode core body exposed portion 4, a positive electrode current collector receiving component (not shown) is connected to a surface opposite to the surface to which the positive electrode current collector 6 is connected. In the wound negative electrode core body exposed portion 5, the negative electrode current collector receiving component 80 is connected to the surface opposite to the surface to which the negative electrode current collector 8 is connected. However, the positive electrode current collector receiving component and the negative electrode current collector receiving component 80 are not essential configurations and may be omitted.

The positive electrode current collector 6 includes a connecting portion 6a connected to the positive electrode core body exposed portion 4, a base portion 6c arranged between the sealing plate 2 and the wound electrode body 3, and a wound electrode body from the base portion 6c. It has a lead portion 6b extending toward 3 and connecting the base portion 6c and the connecting portion 6a. The connecting portion 6a is arranged on the wound positive electrode core body exposed portion 4. The negative electrode current collector 8 includes a connecting portion 8a connected to the negative electrode core body exposed portion 5, a base portion 8c arranged between the sealing plate 2 and the wound electrode body 3, and a wound electrode body from the base portion 8c. It has a lead portion 8b extending toward 3 and connecting the base portion 8c and the connecting portion 8a. The connecting portion 8a is arranged on the wound negative electrode core body exposed portion 5.

The sealing plate 2 is provided with a gas discharge valve 15 that breaks when the pressure inside the square exterior body 1 exceeds a predetermined value and discharges the gas inside the square exterior body 1 to the outside of the square exterior body 1. .. Further, the sealing plate 2 is provided with an electrolytic solution injection hole, and the electrolytic solution injection hole is sealed by a sealing plug 16.

Next, the assembled battery 100 including the plurality of square secondary batteries 20 will be described.

FIG. 3 is a perspective view of the assembled battery 100. Ten square secondary batteries 20 are arranged between the pair of metal end plates 101. The pair of end plates 101 are connected by a metal bind bar 102. The bind bar 102 is fixed to the end plate 101 by bolts 103. In the assembled battery 100, two bind bars 102 are arranged on one side surface, and two bind bars 102 are arranged on the other side surface.

A resin spacer 60 is arranged between the adjacent square secondary batteries 20. The square secondary batteries 20 are arranged so that the first side walls 1b face each other via the spacer 60. The positive electrode terminal 7 of the square secondary battery 20 is electrically connected to the negative electrode terminal 9 of the adjacent square secondary battery 20 by a metal bus bar 104. The assembled battery 100 has a structure in which each spacer 60 presses the first side wall 1b of the square exterior body 1 of each of the opposite square secondary batteries 20.

Next, a method of manufacturing the square secondary battery 20 will be described.

[Manufacturing of positive electrode plate]
_{LiNi 0.35} Co _0.35 Mn _0.30 O ₂ as the positive electrode active material, polyvinylidene fluoride (PVdF) as the binder, carbon black as the conductive agent, and N-methyl-2- as the dispersion medium. Pyrrolidone (NMP) is kneaded so that the mass ratio of positive electrode active material: binder: conductive agent is 91: 7: 2 to prepare a positive electrode active material mixture slurry.

A positive electrode active material mixture slurry is applied to both sides of an aluminum foil having a thickness of 15 μm as a positive electrode core by a die coater. Then, the positive electrode active material mixture slurry is dried to remove NMP in the positive electrode active material mixture slurry. As a result, a positive electrode active material mixture layer is formed. Then, the positive electrode active material mixture layer is compressed by a compression roller so as to have a predetermined packing density. Then, it is cut into a predetermined shape to form a positive electrode plate 40.

Here, the packing density of the positive electrode active material mixture layer after the compression treatment was set to 2.5 g / cm ³ . The length of the positive electrode plate 40 was 440 cm, and the width of the positive electrode plate 40 was 13 cm. Further, in the positive electrode plate 40, the width of the positive electrode active material mixture layer 40b was set to 11 cm.

FIG. 4 is a plan view of the positive electrode plate 40. The positive electrode plate 40 includes a long positive electrode core body 40a and a positive electrode active material mixture layer 40b formed on both sides of the positive electrode core body 40a. The positive electrode core body 40a is provided with a positive electrode core body exposed portion 4 having no positive electrode active material mixture layer 40b formed on both sides along the longitudinal direction at the end portion in the width direction.

[Manufacturing of negative electrode plate]
Graphite as the negative electrode active material, styrene butadiene rubber (SBR) as the binder, carboxymethyl cellulose (CMC) as the thickener, and water, the mass ratio of the negative electrode active material: binder: thickener is 98. Knead so that the ratio is 1: 1 to prepare a negative electrode active material mixture slurry.

A negative electrode active material mixture slurry is applied to both sides of a copper foil having a thickness of 8 μm as a negative electrode core by a die coater. Then, the negative electrode active material mixture slurry is dried to remove water in the negative electrode active material mixture slurry. As a result, the negative electrode active material mixture layer is formed. Then, the negative electrode active material mixture layer is compressed by a compression roller so as to have a predetermined filling density. Then, it is cut into a predetermined shape to form a negative electrode plate 50.

Here, the packing density of the negative electrode active material mixture layer after the compression treatment was set to 1.1 g / cm ³ . The length of the negative electrode plate 50 was 460 cm, and the width of the negative electrode plate 50 was 13 cm. Further, in the negative electrode plate 50, the width of the negative electrode active material mixture layer 50b was set to 12 cm.

FIG. 5 is a plan view of the negative electrode plate 50. The negative electrode plate 50 includes a long negative electrode core body 50a and a negative electrode active material mixture layer 50b formed on both sides of the negative electrode core body 50a. The negative electrode core body 50a is provided with a negative electrode core body exposed portion 5 at the end portion in the width direction in which the negative electrode active material mixture layer 50b is not formed on both sides along the longitudinal direction.

[Manufacturing of wound electrode body]
The long positive electrode plate 40 and the long negative electrode plate 50 produced by the above method are wound through a long polypropylene / polyethylene / polypropylene three-layer separator having a thickness of 20 μm and pressed flat. Mold. The obtained flat wound electrode body 3 has a positive electrode core body exposed portion 4 wound on one side in the direction in which the winding shaft extends, and a negative electrode core body exposed portion wound around the other end portion. Has 5.

The length of the flat wound electrode body 3 in the direction in which the winding shaft extends was set to 140 mm. Further, the length of the flat wound electrode body 3 in the direction perpendicular to the direction in which the winding axis extends was set to 58 mm. Further, the thickness of the flat wound electrode body 3 was set to 15 mm. The number of turns of the positive electrode plate 40 was set to 80. As described above, the width of the positive electrode active material mixture layer 40b is smaller than the width of the negative electrode active material mixture layer 50b. Therefore, the width of the power generation unit (the length in the direction in which the winding shaft extends) is 11 cm, which is the same as the width of the positive electrode active material mixture layer 40b.

[Adjustment of non-aqueous electrolyte]
A mixed solvent was prepared by mixing ethylene carbonate (EC), ethyl methyl carbonate (EMC), and diethyl carbonate (DEC) at a volume ratio (25 ° C., 1 atm) of 30:30:40. _{LiPF 6} was added to this mixed solvent so as to be 1 mol / L. Further, vinylene carbonate (VC) was added so that the addition amount was 0.3% by mass with respect to the total mass of the non-aqueous electrolyte solution, and the addition amount was 1% by mass with respect to the total mass of the non-aqueous electrolyte solution. Lithium bisoxalatobolate was added so as to be.

[Attachment of parts to the sealing plate]
The external insulating member 10 is arranged on the outer surface side of the battery around the positive electrode terminal mounting hole (not shown) provided in the sealing plate 2. The internal insulating member 11 and the base portion 6c of the positive electrode current collector 6 are arranged on the inner surface side of the battery around the positive electrode terminal mounting hole (not shown) provided in the sealing plate 2. Then, the positive electrode terminal 7 is inserted from the outer side of the battery into the through hole of the outer side insulating member 10, the positive electrode terminal mounting hole, the through hole of the inner side insulating member 11, and the through hole of the base portion 6c of the positive electrode current collector 6. The tip of the positive electrode terminal 7 is crimped onto the base portion 6c of the positive electrode current collector 6. As a result, the positive electrode terminal 7 and the positive electrode current collector 6 are fixed to the sealing plate 2. Further, it is preferable to weld the positive electrode terminal 7 and the base portion 6c.

The external insulating member 12 is arranged on the outer surface side of the battery around the negative electrode terminal mounting hole (not shown) provided in the sealing plate 2. The internal insulating member 13 and the base portion 8c of the negative electrode current collector 8 are arranged on the inner surface side of the battery around the negative electrode terminal mounting holes (not shown) provided in the sealing plate 2. Then, the negative electrode terminal 9 is inserted into the through hole of the external insulating member 12, the negative electrode terminal mounting hole, the through hole of the internal insulating member 13, and the through hole of the base portion 8c of the negative electrode current collector 8 from the outside of the battery. The tip of the negative electrode terminal 9 is crimped onto the base 8c of the negative electrode current collector 8. As a result, the negative electrode terminal 9 and the negative electrode current collector 8 are fixed to the sealing plate 2. Further, it is preferable to weld the negative electrode terminal 9 and the base portion 8c.

[Attachment of current collector to wound electrode body]
FIG. 6 is a view showing a surface of the flat wound electrode body 3 to which the positive electrode current collector 6 and the negative electrode current collector 8 are connected. As shown in FIG. 6, the positive electrode current collector 6 is connected to the outer surface of the wound positive electrode core body exposed portion 4. By welding, a positive electrode joint portion 90 is formed between the positive electrode current collector 6 and the positive electrode core body exposed portion 4. The negative electrode current collector 8 is connected to the outer surface of the wound negative electrode core body exposed portion 5. A negative electrode bonding portion 91 is formed in the negative electrode current collector 8 and the negative electrode core body exposed portion 5 by welding. The connection method is, for example, resistance welding, ultrasonic welding, or the like. When resistance welding is performed, the positive electrode current collector receiving component is connected to the outer surface opposite to the outer surface to which the positive electrode current collector 6 is connected in the wound positive electrode core body exposed portion 4, and the positive electrode current collector receiving component is wound. It is preferable to connect the negative electrode current collector receiving component 80 to the outer surface opposite to the outer surface to which the negative electrode current collector 8 is connected in the negative electrode core body exposed portion 5.

[Assembly of square secondary battery]
The flat wound electrode body 3 is covered with the resin sheet 14 and inserted into the square exterior body 1. Then, the sealing plate 2 and the square exterior body 1 are welded, and the opening of the square exterior body 1 is sealed by the sealing plate 2. After that, the non-aqueous electrolytic solution is injected from the electrolytic solution injection hole provided in the sealing plate 2, and the electrolytic solution injection hole is sealed by the sealing plug 16. As a result, the square secondary battery 20 is manufactured. The battery capacity of the square secondary battery 20 was set to 8 Ah.

[For each region in the flat wound electrode body]
As shown in FIG. 6, the positive electrode current collector 6 is joined to the outer surface of the wound positive electrode core body exposed portion 4 by welding, and the positive electrode joint portion 90 is formed. The negative electrode current collector 8 is joined to the outer surface of the wound negative electrode core body exposed portion 5 by welding, and the negative electrode joint portion 91 is formed. The positive electrode bonding portion 90 and the negative electrode bonding portion 91 are formed by resistance welding, ultrasonic welding, irradiation of energy rays such as a laser, and the like. The positive electrode joint 90 is formed over the entire region of the positive electrode core in the stacking direction. That is, the wound positive electrode core body exposed portion 4 is bundled together by the positive electrode joint portion 90. The negative electrode bonding portion 91 is formed over the entire region in the stacking direction of the negative electrode core body. That is, the wound negative electrode core body exposed portion 5 is bundled together by the negative electrode joint portion 91.

In the direction perpendicular to the bottom 1a of the square exterior body 1 (vertical direction in FIG. 6), the center of the positive electrode joint 90 is located closer to the sealing plate 2 than the center line 3x of the wound electrode body 3. Further, in the direction perpendicular to the bottom portion 1a of the square exterior body 1 (vertical direction in FIG. 6), the center of the negative electrode joint portion 91 is located closer to the sealing plate 2 than the center line 3x of the wound electrode body 3. To do. With such a configuration, the conductive path between the positive electrode plate 40 and the positive electrode terminal 7 and the conductive path between the negative electrode plate 50 and the negative electrode terminal 9 are shortened, resulting in a square secondary battery having more excellent output characteristics. ..

The flat wound electrode body 3 has a power generation unit 3a in which a positive electrode active material mixture layer 40b and a negative electrode active material mixture layer 50b are laminated via a separator at the central portion in the direction in which the winding shaft extends. The power generation unit 3a has a flat portion 3b having a flat outer surface, a first curved portion 3c having a curved outer surface located on the sealing plate 2 side, and a curved outer surface located on the bottom 1a side of the square exterior body 1. It has a second curved portion 3d. The boundary between the first curved portion 3c and the flat portion 3b is defined as the first boundary portion 25. The first boundary portion 25 extends in the direction in which the winding axis extends. The boundary between the second curved portion 3d and the flat portion 3b is defined as the second boundary portion 26. The second boundary portion 26 extends in the direction in which the winding shaft extends.

Let L1 be the distance between the end of the positive electrode joint 90 on the sealing plate 2 side and the first boundary 25 in the direction perpendicular to the bottom 1a of the square exterior body 1. Of the power generation unit 3a, 0.25 × L1 to 0. From the end of the positive electrode joint 90 on the sealing plate 2 side toward the first boundary 25 in the direction perpendicular to the bottom 1a of the square exterior body 1. The area up to 75 × L1 is defined as the first region A.

In the direction perpendicular to the bottom portion 1a of the square exterior body 1, the distance between the end portion of the negative electrode joint portion 91 on the negative electrode side on the sealing plate 2 side and the first boundary portion 25 is L2. Of the power generation unit 3a, 0.25 × L2 to 0. From the end portion of the negative electrode joint portion 91 on the sealing plate 2 side toward the first boundary portion 25 in the direction perpendicular to the bottom portion 1a of the square exterior body 1. The area up to 75 × L2 is defined as the second region B.

In the square secondary battery 20 according to the embodiment, the end of the positive electrode joint 90 on the sealing plate 2 side and the sealing plate 2 side of the negative electrode joint 91 in the direction perpendicular to the bottom 1a of the square exterior body 1. The position of the end of is the same. Therefore, the first region A and the second region B are the same region.

Let L3 be the distance between the end of the positive electrode joint 90 on the bottom 1a side and the second boundary 26 in the direction perpendicular to the bottom 1a of the square exterior body 1. 0.25 × L3 to 0.75 from the end of the positive electrode joint 90 on the bottom 1a side toward the second boundary 26 in the direction perpendicular to the bottom 1a of the square exterior body 1 of the power generation unit 3a. The area up to × L3 is defined as the third region C.

Let L4 be the distance between the end of the negative electrode joint 91 on the bottom 1a side and the second boundary 26 in the direction perpendicular to the bottom 1a of the square exterior body 1. 0.25 × L4 to 0.75 from the end of the negative electrode joint 91 on the bottom 1a side toward the second boundary 26 in the direction perpendicular to the bottom 1a of the square exterior body 1 of the power generation unit 3a. The area up to × L4 is defined as the fourth region D.

In the square secondary battery 20 according to the embodiment, the end of the positive electrode joint 90 on the bottom 1a side and the end of the negative electrode joint 91 on the bottom 1a side in the direction perpendicular to the bottom 1a of the square exterior body 1. The positions of the parts are the same. Therefore, the third region C and the fourth region D are the same region.

In the flat wound electrode body 3, the inventor describes a region at a specific distance from the positive electrode junction 90 of the positive electrode core body exposed portion 4 and the positive electrode current collector 6, and the negative electrode core body exposed portion 5 and the negative electrode current collector. It has been found that a region at a specific distance from the negative electrode joint portion 91 of the body 8 is more likely to expand due to charging / discharging or the like than other regions. More specifically, in the flat wound electrode body 3, the above-mentioned first region A, second region B, third region C and fourth region expand in particular due to charging / discharging or the like as compared with other regions. I found it easy to do.

The cause of this is considered as follows. The flat wound electrode body 3 expands as the charge / discharge cycle progresses due to reasons such as cracking of the active material, expansion of the active material, and accumulation of deposits on the negative electrode active material layer. Here, in the flat wound electrode body 3, the positive electrode bonding portion 90 and the negative electrode bonding portion 91 are in a state in which the positive electrode plate 40 and the negative electrode plate 50 are more strongly restrained in the stacking direction in the vicinity thereof. Therefore, in the flat wound electrode body 3, expansion is suppressed in the vicinity of the positive electrode joint 90 and the negative electrode joint 91. Further, in the first curved portion 3c and the second curved portion 3d, the positive electrode plate 40 and the negative electrode plate 50 are laminated in a curved state, and it is difficult to expand in this region. Therefore, strain is accumulated between the vicinity of the positive electrode joint 90 and the negative electrode joint 91 where expansion is suppressed and between the first curved portion 3c and the second curved portion 3d, respectively, and the direction is perpendicular to the winding axis. In (the direction perpendicular to the bottom portion 1a of the square exterior body 1), it is considered that the portions separated from the positive electrode joint portion 90 and the negative electrode joint portion 91 by a predetermined distance are likely to expand.

Therefore, in the assembled battery 100 according to the embodiment, when viewed from a direction perpendicular to one first side wall 1b of the square exterior body 1, the first side wall 1b of the square secondary battery 20 is wound in a flat shape. The increase in reaction force is suppressed by substantially not pressing the region of the electrode body 3 that overlaps with each of the above-mentioned first region A, second region B, third region C, and fourth region D by the spacer 60. ..

In the assembled battery 100 according to the embodiment, a resin spacer 60 as shown in FIG. 7 is arranged between adjacent square secondary batteries 20. In the spacer 60, an upper recess 61 is provided at a position corresponding to the first region A and the second region B of the wound electrode body 3. The upper recesses are provided on both sides of the spacer 60. In the spacer 60, a lower recess 62 is provided at a position corresponding to the third region C and the fourth region D of the wound electrode body 3. The lower recess 62 is provided on both sides of the spacer 60. Therefore, in the assembled battery 100, when viewed from a direction perpendicular to one first side wall 1b of the square exterior body 1, the first side wall 1b has the first area A, the second area B, and the third area. The region overlapping at least one of C and the fourth region D is not pressed by the spacer 60.

In the assembled battery 100, an increase in the reaction force can be suppressed even when the charge / discharge cycle of the square secondary battery 20 is advanced. Therefore, it becomes a more reliable assembled battery.

When viewed from a direction perpendicular to one first side wall 1b of the square exterior body 1, the first side wall 1b has a first region A, a second region B, a third region C, and a fourth region D. It is not necessary that the region overlapping at least one of the above is not completely pressed by the spacer 60. For example, when viewed from a direction perpendicular to one first side wall 1b of the square exterior body 1, a spacer among the regions overlapping at least one of the first region A and the second region B in one first side wall 1b. The region pressed by 60 is preferably 20% or less, more preferably 10% or less, and even more preferably 5% or less. When viewed from a direction perpendicular to one first side wall 1b of the square exterior body 1, the spacer 60 of the region overlapping at least one of the third region C and the fourth region D in one first side wall 1b The pressed region is preferably 20% or less, more preferably 10% or less, and even more preferably 5% or less.

When viewed from a direction perpendicular to one of the pair of first side walls 1b, one of the pair of first side walls 1b overlaps with the flat portion 3b of the power generation unit 3a, and the first area A and the second area Of the regions that do not overlap with B, the third region C, and the fourth region D, the area of the region pressed by the spacer 60 overlaps with the flat portion 3b of the power generation unit 3a in one of the pair of first side walls 1b. It is preferably 70% or more, more preferably 80% or more of the area of the region that does not overlap with the first region A, the second region B, the third region C, and the fourth region D.

When viewed from a direction perpendicular to the other of the pair of first side walls 1b, the other of the pair of first side walls 1b overlaps with the flat portion 3b of the power generation unit 3a, and the first region A and the second region Of the regions that do not overlap with B, the third region C, and the fourth region D, the area of the region pressed by the spacer 60 overlaps with the flat portion 3b of the power generation unit 3a at the other of the pair of first side walls 1b. It is preferably 70% or more, more preferably 80% or more of the area of the region that does not overlap with the first region A, the second region B, the third region C, and the fourth region D.

An upward pressing portion 63, a central pressing portion 64, and a downward pressing portion 65 are provided on both sides of the spacer 60, respectively. Then, the upward pressing portion 63, the central pressing portion 64, and the downward pressing portion 65 each press the first side wall 1b of the square exterior body 1. It is preferable that wall portions 66 for preventing the displacement of the square secondary battery 20 are provided at the four corners of the spacer 60.

Samples 1 to 4 were prepared using the square secondary battery 20 according to the above-described embodiment, and the following tests were performed. The size of the square secondary battery 20 was 148 mm in width, 65 mm in height, and 17.5 mm in thickness. Further, as the square secondary battery 20 used for Samples 1 to 4, a battery that is once charged to a charging depth (SOC) of 100% and then discharged to a charging depth of 20% is used.

First, the common configuration of Samples 1 to 4 will be described with reference to FIG. FIG. 8 is a side view of Samples 1 to 4. In the first pressing jig 160, a polypropylene first pressing portion 160a having a thickness of 2 mm and a polypropylene second pressing portion 160b having a thickness of 2 mm are spaced apart from each other on one surface of a stainless steel plate having a thickness of 13 mm. It is glued. In the second pressing jig 161, a 3rd pressing portion 161a made of polypropylene having a thickness of 2 mm and a 4th pressing portion 161b made of polypropylene having a thickness of 2 mm are spaced apart from each other on one surface of a stainless steel plate having a thickness of 13 mm. It is glued.

The first pressing portion 160a, the second pressing portion 160b, the third pressing portion 161a, and the fourth pressing portion 161b extend in the direction in which the winding axis of the flat wound electrode body 3 extends. In the direction in which the winding shaft of the flat wound electrode body 3 extends, the lengths of the first pressing portion 160a, the second pressing portion 160b, the third pressing portion 161a, and the fourth pressing portion 161b are flat. It is longer than the length of the wound electrode body 3.

The first pressing jig 160 is arranged so that the first side wall 1b of one of the square secondary batteries 20 is in contact with the first pressing portion 160a and the second pressing portion 160b. The second pressing jig 161 is arranged so that the other first side wall 1b of the square secondary battery 20 is in contact with the third pressing portion 161a and the fourth pressing portion 161b. Then, on the surface side of the second pressing jig 161 opposite to the surface on which the third pressing portion 161a and the fourth pressing portion 161b are arranged, a stainless steel intermediate plate 171 having a thickness of 15 mm and a load cell 172 (Minebea Co., Ltd.) A stainless steel base plate 170 having a thickness of 19 mm is arranged via a molding model CMP1-2T). Then, bolts 173 are inserted into through holes provided at the four corners of the first pressing jig 160, the second pressing jig 161 and the base plate 170, and the members are collectively fixed by the nuts 174. Here, the load applied to the load cell 172 is measured when the distance between the first pressing portion 160a of the first pressing jig 160 and the third pressing portion 161a of the second pressing jig 161 is 17.3 mm, and each of them is measured. The initial reaction force of the sample was used.

Samples 1 to 4 described below are the positions of the first pressing portion 160a and the second pressing portion 160b of the first pressing jig 160, the third pressing portion 161a and the fourth pressing portion 161 of the second pressing jig 161.
It has the same structure except that the position of b is different.

[Sample 1]
FIG. 9 is a cross-sectional view of a cross section parallel to the second side wall 1c of the square secondary battery 20, the first pressing jig 160, and the second pressing jig 161 of the sample 1. In sample 1, the first pressing portion 160a and the third pressing portion 161a cause the end of the positive electrode joint 90 on the sealing plate 2 side and the positive electrode joint 90 in the power generation portion 3a of the flat wound electrode body 3. The area between the end on the sealing plate 2 side and the position of 0.25 × L1 is pressed. Here, as described above, L1 is the distance from the end portion of the positive electrode joint portion 90 on the sealing plate 2 side to the first boundary portion 25. Further, in the sample 1, the second pressing portion 160b and the fourth pressing portion 161b cause the end portion of the positive electrode joint 90 on the bottom 1a side and the positive electrode junction 90 in the power generation portion 3a of the flat wound electrode body 3. The area between the end of the bottom 1a side and the position of 0.25 × L3 is pressed. Here, L3 is the distance from the end of the positive electrode joint 90 on the bottom 1a side to the second boundary 26, as described above.

[Sample 2]
FIG. 10 is a cross-sectional view of a cross section parallel to the second side wall 1c of the square secondary battery 20, the first pressing jig 160, and the second pressing jig 161 of the sample 2. In the sample 2, the first pressing portion 160a and the third pressing portion 161a make 0.75 × L1 from the end portion of the positive electrode joint 90 on the sealing plate 2 side in the power generation portion 3a of the flat wound electrode body 3. The region between the position and the position of the positive electrode joint 90 on the sealing plate 2 side to the position of L1 (first boundary portion 25) is pressed. Further, the second pressing portion 160b and the fourth pressing portion 161b provide a position of 0.75 × L3 from the end portion of the positive electrode joint 90 on the bottom 1a side in the power generation portion 3a of the flat wound electrode body 3. The region between the end of the positive electrode joint 90 on the bottom 1a side and the position of L3 (second boundary 26) is pressed.

[Sample 3]
FIG. 11 is a cross-sectional view of a cross section parallel to the second side wall 1c of the square secondary battery 20, the first pressing jig 160, and the second pressing jig 161 of the sample 3. In sample 3, the first pressing portion 160a and the third pressing portion 161a form a 0.25 × L1 portion of the positive electrode joint 90 from the end of the sealing plate 2 side in the power generation portion 3a of the flat wound electrode body 3. The region between the position and the position of 0.50 × L1 from the end of the positive electrode joint 90 on the sealing plate 2 side is pressed. Further, the second pressing portion 160b and the fourth pressing portion 161b provide a position of 0.25 × L3 from the end portion of the positive electrode joint 90 on the bottom 1a side in the power generation portion 3a of the flat wound electrode body 3. The region between the end of the positive electrode joint 90 on the bottom 1a side and the position of 0.50 × L3 is pressed.

[Sample 4]
FIG. 12 is a cross-sectional view of a cross section parallel to the second side wall 1c of the square secondary battery 20, the first pressing jig 160, and the second pressing jig 161 of the sample 4. In the sample 4, the first pressing portion 160a and the third pressing portion 161a make 0.50 × L1 from the end portion of the positive electrode joint 90 on the sealing plate 2 side in the power generation portion 3a of the flat wound electrode body 3. The region between the position and the position of 0.75 × L1 from the end of the positive electrode joint 90 on the sealing plate 2 side is pressed. Further, the second pressing portion 160b and the fourth pressing portion 161b provide a position of 0.50 × L3 from the end portion of the positive electrode joint 90 on the bottom 1a side in the power generation portion 3a of the wound electrode body 3, and the positive electrode joint portion. The area between the end of the 90 on the bottom 1a side and the position of 0.75 × L3 is pressed.

<Initial reaction force>
Table 1 shows the initial reaction forces of Samples 1 to 4 measured by the above method. In Table 1, the initial reaction force of the sample 3 is set to 100, and the initial reaction force of the other samples is shown as a relative numerical value.

As in sample 3, between the position of 0.25 × L1 from the end of the positive electrode joint 90 on the sealing plate 2 side and the position of 0.50 × L1 from the end of the positive electrode joint 90 on the sealing plate 2 side. Is pressed, and between the position of 0.25 × L3 from the end of the positive electrode joint 90 on the bottom 1a side and the position of 0.50 × L3 from the end of the positive electrode joint 90 on the bottom 1a side. When the area is pressed, the initial reaction force is large. Further, as in sample 4, the position of 0.50 × L1 from the end of the positive electrode joint 90 on the sealing plate 2 side and the position of 0.75 × L1 from the end of the positive electrode joint 90 on the sealing plate 2 side. The area between the positive electrode joints 90 is pressed between the position of 050 × L3 from the end of the positive electrode joint 90 on the bottom 1a side and the position of 0.75 × L3 from the end of the positive electrode joint 90 on the bottom 1a side. Even when the region is pressed, the initial reaction force is relatively large.

Like Sample 1 and Sample 2, the position of 0.25 × L1 from the end of the positive electrode joint 90 on the sealing plate 2 side and 0.75 × L1 from the end of the positive electrode joint 90 on the sealing plate 2 side. The region between the positions is not pressed, and the position of 0.25 × L3 from the end of the positive electrode joint 90 on the bottom 1a side and the position of 0.75 × L3 from the end of the positive electrode joint 90 on the bottom 1a side. It can be seen that the initial reaction force can be suppressed low when the region between and is not pressed.

Here, the initial increase in reaction force is considered to be due to the following factors. First, in the process of assembling the square secondary battery 20, the member constituting the wound electrode body 3 expands due to the infiltration of the non-aqueous electrolytic solution into the wound electrode body 3. For example, it is conceivable that the binder contained in the positive electrode active material mixture layer and the negative electrode active material mixture layer swells due to the non-aqueous electrolytic solution. Further, since the square secondary battery 20 has undergone a charging process, it is considered that the wound electrode body 3 expands due to the formation of a film on the active material mixture layer, the expansion of the active material mixture layer, and the like.

The degree of expansion of the wound electrode body 3 differs depending on each region of the wound electrode body 3. Therefore, as described above, the initial reaction force also differs greatly depending on the position where the square secondary battery 20 is pressed. Therefore, in the present invention, the reaction force can be reduced by not pressing the specific region with reference to the joint portion between the current collector and the exposed core body.

Here, in the flat wound electrode body 3, the positive electrode bonding portion 90 and the negative electrode bonding portion 91 are in a state in which the positive electrode plate 40 and the negative electrode plate 50 are more strongly restrained in the stacking direction in the vicinity thereof. Therefore, in the flat wound electrode body 3, expansion is suppressed in the vicinity of the positive electrode joint 90 and the negative electrode joint 91. Further, in the first curved portion 3c and the second curved portion 3d, the positive electrode plate 40 and the negative electrode plate 50 are laminated in a curved state, and it is difficult to expand in this region. Therefore, strain is accumulated between the vicinity of the positive electrode joint 90 and the negative electrode joint 91 where expansion is suppressed and between the first curved portion 3c and the second curved portion 3d, respectively, and the direction is perpendicular to the winding axis. In (the direction perpendicular to the bottom portion 1a of the square exterior body 1), it is considered that the portions separated from the positive electrode joint portion 90 and the negative electrode joint portion 91 by a predetermined distance are likely to expand.

When viewed from a direction perpendicular to the first side wall 1b, the area of the first side wall 1b that overlaps the flat portion 3b and is 0.25 × from the end of the positive electrode joint 90 on the sealing plate 2 side. It is preferable that the region overlapping the position of L1 and the region between the end of the positive electrode joint 90 on the sealing plate 2 side and the position of 0.50 × L1 is not substantially pressed by the spacer 60. For example, it is preferable that 95% or more of the region is not pressed by the spacer 60. Further, when viewed from a direction perpendicular to the first side wall 1b, the area of the first side wall 1b that overlaps with the flat portion 3b and is 0.25 × L3 from the end of the positive electrode joint 90 on the bottom 1a side. It is preferable that the region overlapping the region between the position of 1 and the position of 0.50 × L3 from the end of the positive electrode joint 90 on the bottom 1a side is not substantially pressed by the spacer 60. For example, it is preferable that 95% or more of the region is not pressed by the spacer 60.

<Reaction force after charge / discharge cycle>
A charge / discharge cycle test was performed on samples 5 and 6. The configurations of Sample 5 and Sample 6 are as follows.

[Sample 5]
In sample 5, except that the configurations of the first pressing jig 160 regarding the first pressing portion 160a and the second pressing portion 160b and the configurations of the second pressing jig 161 regarding the third pressing portion 161a and the fourth pressing portion 161b are different. It has the same structure as the above-mentioned samples 1 to 4. In sample 5, the first pressing jig 160 is provided with two first pressing portions 160a and two second pressing portions 160b, and the second pressing jig 161 is provided with two third pressing portions 161a and two fourth pressing portions. 161b was provided. Then, the pair of first side walls 1b of the square secondary battery 20 press the pressed positions in the sample 1 and the sample 2, respectively. That is, in the power generation portion 3a of the flat wound electrode body 3, a position of 0.25 × L1 from the end portion of the positive electrode joint portion 90 on the sealing plate 2 side and the end portion of the positive electrode joint portion 90 on the sealing plate 2 side. The region between the positive electrode joint 90 and the position of 0.75 × L1 from the end of the positive electrode joint 90 on the sealing plate 2 side and the position of L1 from the end of the positive electrode joint 90 on the sealing plate 2 side (first boundary portion 25). ) And the area between them is pressed. Further, in the power generation portion 3a of the flat wound electrode body 3, the end portion of the positive electrode joint portion 90 on the bottom portion 1a side and the position of 0.25 × L3 from the end portion of the positive electrode joint portion 90 on the bottom portion 1a side. Region between, 0.75 × L3 from the end of the positive electrode joint 90 on the bottom 1a side and the position of L3 from the end of the positive electrode joint 90 on the bottom 1a side (second boundary 26). Was pressed.

[Sample 6]
In sample 6, except that the configurations of the first pressing jig 160 regarding the first pressing portion 160a and the second pressing portion 160b and the configurations of the second pressing jig 161 regarding the third pressing portion 161a and the fourth pressing portion 161b are different. It has the same structure as the above-mentioned samples 1 to 4. In sample 6, the widths of the first pressing portion 160a and the second pressing portion 160b of the first pressing jig 160 are widened, respectively, and the widths of the third pressing portion 161a and the fourth pressing portion 161b of the second pressing jig 161 are widened. It was. Then, the pair of first side walls 1b of the square secondary battery 20 press the pressed positions in the sample 3 and the sample 4, respectively. That is, in the power generation portion 3a of the flat wound electrode body 3, the position of 0.25 × L1 from the end portion of the positive electrode joint portion 90 on the sealing plate 2 side and the end portion of the positive electrode joint portion 90 on the sealing plate 2 side. The area between the positions of 0.75 × L1 was pressed. Further, in the power generation portion 3a of the flat wound electrode body 3, the position of 0.25 × L3 from the end portion of the positive electrode joint portion 90 on the bottom portion 1a side and 0 from the end portion of the positive electrode joint portion 90 on the bottom portion 1a side. The area between the .75 x L3 positions was pressed.

For samples 5 and 6, the distance between the first pressing portion 160a of the first pressing jig 160 and the third pressing portion 161a of the second pressing jig 161 was fixed at 17.6 mm, and under the condition of 55 ° C. The following tests were performed.

<Charge / discharge cycle test>
The charging depth (SOC) of the square secondary battery 20 was adjusted to 30%. Next, a cycle in which 50% of the 1C discharge capacity (capacity when discharging from SOC 100% to 0% at 1C) is charged at 10C and the same capacity is continuously discharged at 10C has a throughput of 100kWh (). It was repeated until the charge / discharge throughput integration) was reached.

The amount of increase in the load applied to the load cell 172 before and after the charge / discharge cycle test was defined as the amount of increase in the reaction force. Table 2 shows the amount of increase in the reaction force of Samples 5 and 6 measured by the above method. In Table 2, the amount of increase in the reaction force of the sample 5 is set to 100, and the amount of increase in the reaction force of the sample 6 is shown as a relative numerical value.

As can be seen from the test results of the sample 6, in the power generation portion 3a of the flat wound electrode body 3, 0.25 × L1 from the end portion of the positive electrode joint portion 90 on the sealing plate 2 side toward the first boundary portion 25. From the position of 0.75 × L1 from the end of the positive electrode joint 90 on the sealing plate 2 side toward the first boundary 25, and from the end of the positive electrode joint 90 on the bottom 1a side. The region between the position of 0.25 × L3 toward the second boundary portion 26 and the position of 0.75 × L3 toward the second boundary portion 26 from the end on the bottom 1a side of the positive electrode joint portion 90 is The degree of expansion is large, and when this region is pressed, the reaction force increases significantly.

In the power generation portion 3a of the flat wound electrode body 3, the position of 0.25 × L1 from the end portion of the positive electrode joint portion 90 on the sealing plate 2 side toward the first boundary portion 25 and the sealing portion of the positive electrode joint portion 90. The region between the position of 0.75 × L1 from the end on the plate 2 side toward the first boundary 25, and the end on the bottom 1a side of the positive electrode joint 90 toward the second boundary 26. In sample 5, which does not press the region between the position of 25 × L3 and the position of 0.75 × L3 from the end of the positive electrode joint 90 on the bottom 1a side toward the second boundary 26, the reaction due to the charge / discharge cycle It can be seen that the increase in force can be suppressed.

[Modification 1]
In the square secondary battery 20 according to the above-described embodiment, the end of the positive electrode joint 90 on the sealing plate 2 side and the sealing plate 2 side of the negative electrode joint 91 in the direction perpendicular to the bottom 1a of the square exterior body 1. The positions of the ends of the positive electrode joints 90 were the same, and the positions of the ends of the positive electrode joint 90 on the bottom 1a side and the ends of the negative electrode joint 91 on the bottom 1a side were the same. In the square secondary battery according to the first modification, the positions of the positive electrode joint 90 and the negative electrode joint 91 are different in the direction perpendicular to the bottom 1a of the square exterior body 1. The square secondary battery according to the first modification has the same configuration as the square secondary battery 20 according to the embodiment except for the positions of the positive electrode joint 90 and the negative electrode joint 91.

FIG. 13 is a diagram showing a surface on the side to which the positive electrode current collector 6 and the negative electrode current collector 8 are connected in the flat wound electrode body 3 of the square secondary battery according to the first modification.

In the direction perpendicular to the bottom portion 1a of the square exterior body 1, the distance between the end portion of the positive electrode joint portion 90 on the sealing plate 2 side and the first boundary portion 25 is L1. Of the power generation unit 3a, 0.25 × L1 to 0. From the end of the positive electrode joint 90 on the sealing plate 2 side toward the first boundary 25 in the direction perpendicular to the bottom 1a of the square exterior body 1. The area up to 75 × L1 is defined as the first region A.

In the direction perpendicular to the bottom portion 1a of the square exterior body 1, the distance between the end portion of the negative electrode joint portion 91 on the sealing plate 2 side and the first boundary portion 25 is L2. Of the power generation unit 3a, 0.25 × L2 to 0. From the end portion of the negative electrode joint portion 91 on the sealing plate 2 side toward the first boundary portion 25 in the direction perpendicular to the bottom portion 1a of the square exterior body 1. The area up to 75 × L2 is defined as the second region B.

Here, in the flat wound electrode body 3, the first region A and the second region B are likely to expand. Therefore, when viewed from a direction perpendicular to one of the pair of first side walls 1b, in one of the pair of first side walls 1b, in a region that overlaps with at least one of the first region A and the second region B. The area of the region pressed by the spacer 60 is preferably 20% or less of the area of one of the pair of first side walls 1b that overlaps with at least one of the first region A and the second region B. It is more preferably% or less, and further preferably 5% or less.

In the direction perpendicular to the bottom portion 1a of the square exterior body 1, the distance between the end portion of the positive electrode joint portion 90 on the bottom portion 1a side and the second boundary portion 26 is L3. 0.25 × L3 to 0.75 from the end of the positive electrode joint 90 on the bottom 1a side toward the second boundary 26 in the direction perpendicular to the bottom 1a of the square exterior body 1 of the power generation unit 3a. The area up to × L3 is defined as the third region C.

In the direction perpendicular to the bottom portion 1a of the square exterior body 1, the distance between the end portion of the negative electrode joint portion 91 on the bottom portion 1a side and the second boundary portion 26 is L4. 0.25 × L4 to 0.75 from the end of the negative electrode joint 91 on the bottom 1a side toward the second boundary 26 in the direction perpendicular to the bottom 1a of the square exterior body 1 of the power generation unit 3a. The area up to × L4 is defined as the fourth region D.

Here, in the flat wound electrode body 3, the third region C and the fourth region D are likely to expand. Therefore, when viewed from a direction perpendicular to one of the pair of first side walls 1b, in one of the pair of first side walls 1b, in a region that overlaps with at least one of the third region C and the fourth region D. The area of the region pressed by the spacer 60 is preferably 20% or less of the area of one of the pair of first side walls 1b that overlaps with at least one of the third region C and the fourth region D. It is more preferably% or less, and further preferably 5% or less.

When viewed from a direction perpendicular to one of the pair of first side walls 1b, one of the pair of first side walls 1b overlaps with the flat portion 3b of the power generation unit 3a, and the first area A and the second area Of the regions that do not overlap with B, the third region B, and the fourth region D, the area of the region pressed by the spacer 60 overlaps with the flat portion 3b of the power generation unit 3a in one of the pair of first side walls 1b. It is preferably 70% or more, more preferably 80% or more of the area of the region that does not overlap with the first region A, the second region B, the third region B, and the fourth region D.

[Modification 2]
FIG. 14 is a diagram showing a surface on the side to which the positive electrode current collector 6 and the negative electrode current collector 8 are connected in the flat wound electrode body 3 of the square secondary battery according to the modified example 2. The square secondary battery according to the modified example 2 has the same structure as the square secondary battery according to the modified example 1.

As shown in FIG. 14, in the direction in which the winding shaft of the flat wound electrode body 3 extends (left-right direction in FIG. 14), the width of the flat portion 3b of the power generation portion 3a of the flat wound electrode body 3 is adjusted. Let it be W1. Then, in the direction in which the winding axis extends, between the position of 0.25 × W1 on one side from the center line of the flat portion 3b and the position of 0.25 × W1 on the other side from the center line of the power generation unit 3a. Let the area be the fifth area. Then, when viewed from a direction perpendicular to one of the first side walls 1b, the area of one first side wall 1b that overlaps with at least one of the first region A and the second region B and overlaps with the fifth region, that is, one. Of the region overlapping with at least one of A1 and B1 in FIG. 14 on the first side wall 1b, the area of the region pressed by the spacer 60 is at least one of the first region A and the second region B on the first side wall 1b. It is preferably 5% or less of the area of the region that overlaps with one and overlaps with the fifth region.

Further, when viewed from a direction perpendicular to one of the first side walls 1b, the area of one first side wall 1b that overlaps with at least one of the third region C and the fourth region D and overlaps with the fifth region, that is, one. Of the region overlapping with at least one of C1 and D1 in FIG. 14 on the first side wall 1b, the area of the region pressed by the spacer 60 is at least one of the first region A and the second region B on the first side wall 1b. It is preferably 5% or less of the area of the region that overlaps with one and overlaps with the fifth region.

Further, when viewed from a direction perpendicular to the other first side wall 1b, the area of the other first side wall 1b that overlaps with at least one of the first region A and the second region B and overlaps with the fifth region, that is, the figure. Of the regions overlapping with at least one of A1 and B1 in 14, the area of the region pressed by the spacer overlaps with at least one of the first region A and the second region B on the other first side wall 1b and overlaps with the fifth region. It is preferably 5% or less of the area of the overlapping region.

Further, when viewed from a direction perpendicular to the other first side wall 1b, the area of the other first side wall 1b that overlaps with at least one of the third region C and the fourth region D and overlaps with the fifth region, that is, the figure. Of the regions overlapping with at least one of C1 and D1 in 14, the area of the region pressed by the spacer overlaps with at least one of the third region C and the fourth region D on the other first side wall 1b and overlaps with the fifth region. It is preferably 5% or less of the area of the overlapping region.

Further, when viewed from a direction perpendicular to one of the first side walls 1b, the area of the one first side wall 1b that overlaps with the flat portion 3b and does not overlap with any of the area A1, the area B1, the area C1 and the area D1. The area pressed by the spacer is 70% or more of the area of the area that overlaps with the flat portion 3b on one of the first side walls 1b and does not overlap with any of the area A1, the area B1, the area C1 and the area D1. preferable.

Further, when viewed from a direction perpendicular to the other first side wall 1b, the area of the other first side wall 1b that overlaps with the flat portion 3b and does not overlap with any of the area A1, the area B1, the area C1 and the area D1. The area pressed by the spacer is 70% or more of the area of the other first side wall 1b that overlaps with the flat portion 3b and does not overlap with any of the area A1, the area B1, the area C1 and the area D1. preferable.

In the second modification, the spacer 70 as shown in FIG. 15 can be used. An upper recess 71 and a lower recess 72 are provided on both sides of the spacer 70, respectively.

When viewed from a direction perpendicular to one first side wall 1b, a region that overlaps with at least one of the first region A and the second region B and overlaps with the fifth region in one first side wall 1b, that is, one of the first side walls. The upper recess 71 is arranged so as to face the region of one side wall 1b that overlaps with at least one of A1 and B1 of FIG. When viewed from a direction perpendicular to one first side wall 1b, a region that overlaps with at least one of the third region C and the fourth region D and overlaps with the fifth region in one first side wall 1b, that is, one of the first side walls. The lower recess 72 is arranged so as to face the region of one side wall 1b that overlaps with at least one of C1 and D1 of FIG.

The spacer 70 has a pressing portion 73, and the pressing portion 73 presses the first side wall of the square exterior body 1.
It is preferable that wall portions 74 for preventing the displacement of the square secondary battery are provided at the four corners of the spacer 70. Further, the upper recess 71, the lower recess 72, and the pressing portion 73 are provided on both sides of the spacer 70.

[Other]
As each material such as the positive electrode plate, the negative electrode plate, the non-aqueous electrolyte, and the separator, known materials used for the lithium ion secondary battery can be used.

As the positive electrode active material, it is preferable to use a lithium transition metal composite oxide. Examples of the lithium transition metal composite oxide include lithium cobaltate, lithium manganate, lithium nickelate, lithium nickel manganese composite oxide, lithium nickel cobalt composite oxide, and lithium nickel cobalt manganese composite oxide. Further, those obtained by adding Al, Ti, Zr, W, Nb, B, Mg, Mo or the like to the above lithium transition metal composite oxide can also be used.

As the negative electrode active material, it is preferable to use a carbon material capable of occluding and releasing lithium ions. Examples of the carbon material capable of storing and releasing lithium ions include graphite, difficult-to-graphite carbon, easy-to-graphite carbon, fibrous carbon, coke and carbon black. Of these, graphite is particularly preferable. Further, examples of the non-carbon material include silicon, tin, and alloys and oxides mainly composed of them.

As the non-aqueous solvent (organic solvent) of the non-aqueous electrolyte, carbonates, lactones, ethers, ketones, esters and the like can be used, and two or more of these solvents may be mixed and used. it can. For example, cyclic carbonates such as ethylene carbonate, propylene carbonate and butylene carbonate, and chain carbonates such as dimethyl carbonate, ethylmethyl carbonate and diethyl carbonate can be used. In particular, it is preferable to use a mixed solvent of cyclic carbonate and chain carbonate. In addition, unsaturated cyclic carbonates such as vinylene carbonate (VC) can be added to the non-aqueous electrolyte.

As the electrolyte salt of the non-aqueous electrolyte, those generally used as the electrolyte salt in the conventional lithium ion secondary battery can be used. For example, LiPF ₆ , LiBF ₄ , LiCF ₃ SO ₃ , LiN (CF ₃ SO ₂ ) ₂ , LiN (C ₂ F ₅ SO ₂ ) ₂ , LiN (CF ₃ SO ₂ ) (C ₄ F ₉ SO ₂ ), LiC (CF ₃ SO ₂ ) ₃ , LiC (C ₂ F ₅ SO ₂ ) ₃ , LiAsF ₆ , LiClO ₄ , Li ₂ B ₁₀ Cl ₁₀ , Li ₂ B ₁₂ Cl ₁₂ , LiB (C ₂ O ₄ ) ₂ , LiB ( C ₂ O ₄ ) F ₂ , LiP (C ₂ O ₄ ) ₃ , LiP (C ₂ O ₄ ) ₂ F ₂ , LiP (C ₂ O ₄ ) F _{4 and the} like and mixtures thereof are used. Of these, LiPF ₆ is particularly preferable. The amount of the electrolyte salt dissolved in the non-aqueous solvent is preferably 0.5 to 2.0 mol / L.

As the separator, it is preferable to use a resin porous membrane. For example, it is preferable to use a porous membrane made of polyolefin. As the polyolefin, polypropylene (PP), polyethylene (PE) and the like are particularly preferable. Further, a separator having a three-layer structure (PP / PE / PP or PE / PP / PE) of polypropylene (PP) and polyethylene (PE) can also be used. Moreover, you may use a polymer electrolyte as a separator.

The packing density of the positive electrode active material mixture layer ^is preferably ^{1.5g / cm 3 ~4.0g / cm 3} , more preferably ^{2.0g / cm 3 ~3.0g / cm 3} . The packing density of the active material mixture layer ^is preferably ^{0.5g / cm 3 ~2.5g / cm 3} , more preferably ^{0.8g / cm 3 ~1.8g / cm 3} .

The length of the flat wound electrode body in the direction in which the winding axis of the flat wound electrode body extends is preferably 50 mm to 200 mm, more preferably 90 mm to 160 mm. The length of the flat wound electrode body in the direction perpendicular to the winding axis of the flat wound electrode body (the direction perpendicular to the bottom of the square exterior body) may be 50 mm to 100 mm. It is preferably 50 mm to 80 mm, and more preferably 50 mm to 80 mm. The thickness of the flat wound electrode body is preferably 5 mm to 30 mm, more preferably 8 mm to 20 mm.

In the flat wound electrode body, the number of times the positive electrode plate is wound is preferably 20 to 120, and more preferably 30 to 100.

20 ... Square secondary battery 1 ... Square exterior body 1a ... Bottom 1b ... First side wall 1c ... Second side wall 2 ... Seal plate 3 ... Winding electrode body 3a ...・ ・ Power generation part 3b ・ ・ ・ Flat part 3c ・ ・ ・ First curved part 3d ・ ・ ・ Second curved part 25 ・ ・ ・ First boundary part 26 ・ ・ ・ Second boundary part 40 ・ ・ ・ Positive electrode plate 40a ・ ・・ ・ Positive electrode core 40b ・ ・ ・ Positive electrode active material mixture layer 4 ・ ・ ・ Positive electrode core body exposed part 50 ・ ・ ・ Negative electrode plate 50a ・ ・ ・ Negative electrode core body 50b ・ ・ ・ Negative electrode active material mixture layer 5 ・ ・・ Negative electrode core body exposed part 6 ・ ・ ・ Positive electrode current collector 6a ・ ・ ・ Connection part 6b ・ ・ ・ Lead part 6c ・ ・ ・ Base part 7 ・ ・ ・ Positive electrode terminal 8 ・ ・ ・ Negative electrode current collector 8a ・ ・ ・Connection part 8b ... Lead part 8c ... Base part 9 ... Negative electrode terminal 10 ... External side insulating member 11 ... Internal side insulating member 12 ... External side insulating member 13 ... Internal side Insulating member 14 ... Resin sheet 15 ... Gas discharge valve 16 ... Sealing plug 100 ... Assembled battery 101 ... End plate 102 ... Bind bar 103 ... Bolt 104 ... Bus bar 60 ・ ・ ・ Spacer 61 ・ ・ ・ Upper concave part 62 ・ ・ ・ Lower concave part 63 ・ ・ ・ Upper pressing part 64 ・ ・ ・ Central pressing part 65 ・ ・ ・ Lower pressing part 66 ・ ・ ・ Wall part

70 ... Spacer 71 ... Upper recess 72 ... Lower recess 73 ... Pressing part 74 ... Wall part

80 ... Negative electrode current collector receiving parts

90 ... Positive electrode joint 91 ... Negative electrode joint

160 ... 1st pressing jig 160a ... 1st pressing portion 160b ... 2nd pressing portion 161 ... 2nd pressing jig 161a ... 3rd pressing portion 161b ... 4th pressing portion

170 ... Base plate 171 ... Intermediate plate 172 ... Load cell 173 ... Bolt 174 ... Nut

Claims (6)

An assembled battery in which a plurality of square secondary batteries are arranged via spacers.
The square secondary battery is
A flat wound electrode body in which a long positive electrode plate having a positive electrode active material mixture layer and a long negative electrode plate having a negative electrode active material mixture layer are wound via a long separator. When,
A square exterior body having an opening, a bottom, a pair of first side walls, and a pair of second side walls and accommodating the wound electrode body.
A sealing plate for sealing the opening is provided.
The area of the first side wall is larger than the area of the second side wall.
The wound electrode body includes a wound positive electrode core body exposed portion arranged on one side of the pair of second side walls and a wound negative electrode core arranged on the other side of the pair of second side walls. Has a body exposed part,
A positive electrode current collector is joined to the exposed portion of the positive electrode core to form a positive electrode joint.
A negative electrode current collector is joined to the exposed portion of the negative electrode core to form a negative electrode joint.
The wound electrode body has a power generation unit in which the positive electrode active material mixture layer and the negative electrode active material mixture layer are laminated via the separator.
The power generation unit has a flat portion having a flat outer surface, a first curved portion having a curved outer surface and located closer to the sealing plate than the flat portion, and a curved outer surface, which is more than the flat portion. It has a second curved portion located on the bottom side and has a second curved portion.
The boundary between the flat portion and the first curved portion is defined as the first boundary portion, and the boundary between the flat portion and the second curved portion is defined as the second boundary portion.
The distance between the end of the positive electrode joint on the sealing plate side and the first boundary is L1 in the direction perpendicular to the bottom, and the power generation is performed in the direction perpendicular to the bottom. The region of 0.25 × L1 to 0.75 × L1 from the end of the positive electrode joint portion on the sealing plate side toward the first boundary portion is defined as the first region.
The distance between the end of the negative electrode joint on the sealing plate side and the first boundary is L2 in the direction perpendicular to the bottom, and the power generation is performed in the direction perpendicular to the bottom. A region of 0.25 × L2 to 0.75 × L2 from the end of the negative electrode joint portion on the sealing plate side toward the first boundary portion is defined as a second region.
The distance between the bottom-side end of the positive electrode joint and the second boundary in the direction perpendicular to the bottom is L3, and the power generation unit is in the direction perpendicular to the bottom. Of these, the region of 0.25 × L3 to 0.75 × L3 from the bottom end of the positive electrode joint toward the second boundary is defined as the third region.
The distance between the bottom-side end of the negative electrode joint and the second boundary in the direction perpendicular to the bottom is L4, and the power generation unit is in the direction perpendicular to the bottom. Of these, the region of 0.25 × L4 to 0.75 × L4 from the bottom end of the negative electrode joint toward the second boundary is defined as the fourth region.
Of the regions that overlap with at least one of the first region and the second region in one of the pair of first sidewalls when viewed from a direction perpendicular to one of the pair of first sidewalls. The area of the region pressed by the spacer is 20% or less of the area of one of the pair of first side walls that overlaps at least one of the first region and the second region.
Of the regions that overlap with at least one of the third region and the fourth region in one of the pair of first side walls when viewed from a direction perpendicular to one of the pair of first side walls. area of the region which is pressed by the spacer, Ri said third region and der than 20% of the area of the at least one overlaps the region of the fourth region in one of the pair of first side wall,
When viewed from a direction perpendicular to one of the pair of first side walls, one of the pair of first side walls overlaps the flat portion and is between the first region and the third region. The area overlapping the located area is pressed by the spacer, and the area is pressed by the spacer.
When viewed from a direction perpendicular to the other of the pair of first side walls, the other of the pair of first side walls overlaps the flat portion and is between the first region and the third region. The area overlapping the located area was pressed by the spacer.
Batteries assembled. Of the regions that overlap with at least one of the first region and the second region in the other of the pair of first sidewalls when viewed from a direction perpendicular to the other of the pair of first sidewalls. The area of the region pressed by the spacer is 20% or less of the area of the region overlapping at least one of the first region and the second region on the other side of the pair of first side walls.
Of the regions of the other of the pair of first side walls that overlap with at least one of the third region and the fourth region when viewed from a direction perpendicular to the other of the pair of first side walls. The first aspect of the present invention, wherein the area of the region pressed by the spacer is 20% or less of the area of the other of the pair of first side walls that overlaps at least one of the third region and the fourth region. Batteries . An assembled battery in which a plurality of square secondary batteries are arranged via spacers.
The square secondary battery is
A flat wound electrode body in which a long positive electrode plate having a positive electrode active material mixture layer and a long negative electrode plate having a negative electrode active material mixture layer are wound via a long separator. When,
A square exterior body having an opening, a bottom, a pair of first side walls, and a pair of second side walls and accommodating the wound electrode body.
A sealing plate for sealing the opening is provided.
The area of the first side wall is larger than the area of the second side wall.
The wound electrode body includes a wound positive electrode core body exposed portion arranged on one side of the pair of second side walls and a wound negative electrode core arranged on the other side of the pair of second side walls. Has a body exposed part,
A positive electrode current collector is joined to the exposed portion of the positive electrode core to form a positive electrode joint.
A negative electrode current collector is joined to the exposed portion of the negative electrode core to form a negative electrode joint.
The wound electrode body has a power generation unit in which the positive electrode active material mixture layer and the negative electrode active material mixture layer are laminated via the separator.
The power generation unit has a flat portion having a flat outer surface and a curved outer surface, and is more than the flat portion.
It has a first curved portion located on the sealing plate side and a second curved portion having a curved outer surface and located on the bottom side of the flat portion.
The boundary between the flat portion and the first curved portion is defined as the first boundary portion, and the boundary between the flat portion and the second curved portion is defined as the second boundary portion.
The distance between the end of the positive electrode joint on the sealing plate side and the first boundary is L1 in the direction perpendicular to the bottom, and the power generation is performed in the direction perpendicular to the bottom. The region of 0.25 × L1 to 0.75 × L1 from the end of the positive electrode joint portion on the sealing plate side toward the first boundary portion is defined as the first region.
The distance between the end of the negative electrode joint on the sealing plate side and the first boundary is L2 in the direction perpendicular to the bottom, and the power generation is performed in the direction perpendicular to the bottom. A region of 0.25 × L2 to 0.75 × L2 from the end of the negative electrode joint portion on the sealing plate side toward the first boundary portion is defined as a second region.
The distance between the bottom-side end of the positive electrode joint and the second boundary in the direction perpendicular to the bottom is L3, and the power generation unit is in the direction perpendicular to the bottom. Of these, the region of 0.25 × L3 to 0.75 × L3 from the bottom end of the positive electrode joint toward the second boundary is defined as the third region.
The distance between the bottom-side end of the negative electrode joint and the second boundary in the direction perpendicular to the bottom is L4, and the power generation unit is in the direction perpendicular to the bottom. Of these, the region of 0.25 × L4 to 0.75 × L4 from the bottom end of the negative electrode joint toward the second boundary is defined as the fourth region.
Of the regions that overlap with at least one of the first region and the second region in one of the pair of first sidewalls when viewed from a direction perpendicular to one of the pair of first sidewalls. The area of the region pressed by the spacer is 20% or less of the area of one of the pair of first side walls that overlaps at least one of the first region and the second region.
Of the regions that overlap with at least one of the third region and the fourth region in one of the pair of first side walls when viewed from a direction perpendicular to one of the pair of first side walls. The area of the region pressed by the spacer is 20% or less of the area of one of the pair of first side walls that overlaps at least one of the third region and the fourth region.
When viewed from a direction perpendicular to one of the pair of first side walls, one of the pair of first side walls overlaps with the flat portion and the first region, the second region, and the first side wall. Of the three regions and the region that does not overlap with the fourth region, the area of the region pressed by the spacer overlaps with the flat portion in one of the pair of first side walls and the first region and the second. region, the third region and der Ru assembled battery 70% of the area of the region which does not overlap with the fourth region. When viewed from a direction perpendicular to the other of the pair of first side walls, the other of the pair of first side walls overlaps with the flat portion and the first region, the second region, and the first side wall. Of the three regions and the region that does not overlap with the fourth region, the area of the region pressed by the spacer overlaps with the flat portion at the other of the pair of first side walls and the first region and the second. region, the third region and the assembled battery according to claim 3 is 70% or more of an area of the fourth does not overlap with the area region. In the spacer, when viewed from a direction perpendicular to one of the pair of first side walls, one of the pair of first side walls overlaps at least one of the first region and the second region. A first recess is provided in the portion facing the region, and a first recess is provided.
In the spacer, when viewed from a direction perpendicular to one of the pair of first side walls, one of the pair of first side walls overlaps with at least one of the third region and the fourth region. The assembled battery according to any one of claims 1 to 4 , wherein a second recess is provided in a portion facing the region. An assembled battery in which a plurality of square secondary batteries are arranged via spacers.
The square secondary battery is
A flat wound electrode body in which a long positive electrode plate having a positive electrode active material mixture layer and a long negative electrode plate having a negative electrode active material mixture layer are wound via a long separator. When,
A square exterior body having an opening, a bottom, a pair of first side walls, and a pair of second side walls and accommodating the wound electrode body.
A sealing plate for sealing the opening is provided.
The area of the first side wall is larger than the area of the second side wall.
The wound electrode body includes a wound positive electrode core body exposed portion arranged on one side of the pair of second side walls and a wound negative electrode core arranged on the other side of the pair of second side walls. Has a body exposed part,
A positive electrode current collector is joined to the exposed portion of the positive electrode core to form a positive electrode joint.
A negative electrode current collector is joined to the exposed portion of the negative electrode core to form a negative electrode joint.
The wound electrode body has a power generation unit in which the positive electrode active material mixture layer and the negative electrode active material mixture layer are laminated via the separator.
The power generation unit has a flat portion having a flat outer surface, a first curved portion having a curved outer surface and located closer to the sealing plate than the flat portion, and a curved outer surface, which is more than the flat portion. It has a second curved portion located on the bottom side and has a second curved portion.
The boundary between the flat portion and the first curved portion is defined as the first boundary portion, and the boundary between the flat portion and the second curved portion is defined as the second boundary portion.
The distance between the end of the positive electrode joint on the sealing plate side and the first boundary is L1 in the direction perpendicular to the bottom, and the power generation is performed in the direction perpendicular to the bottom. The region of 0.25 × L1 to 0.75 × L1 from the end of the positive electrode joint portion on the sealing plate side toward the first boundary portion is defined as the first region.
The distance between the end of the negative electrode joint on the sealing plate side and the first boundary is L2 in the direction perpendicular to the bottom, and the power generation is performed in the direction perpendicular to the bottom. A region of 0.25 × L2 to 0.75 × L2 from the end of the negative electrode joint portion on the sealing plate side toward the first boundary portion is defined as a second region.
The distance between the bottom-side end of the positive electrode joint and the second boundary in the direction perpendicular to the bottom is L3, and the power generation unit is in the direction perpendicular to the bottom. Of these, the region of 0.25 × L3 to 0.75 × L3 from the bottom end of the positive electrode joint toward the second boundary is defined as the third region.
The distance between the bottom-side end of the negative electrode joint and the second boundary in the direction perpendicular to the bottom is L4, and the power generation unit is in the direction perpendicular to the bottom. Of these, the region of 0.25 × L4 to 0.75 × L4 from the bottom end of the negative electrode joint toward the second boundary is defined as the fourth region.
Of the regions that overlap with at least one of the first region and the second region in one of the pair of first sidewalls when viewed from a direction perpendicular to one of the pair of first sidewalls. The area of the region pressed by the spacer is 20% or less of the area of one of the pair of first side walls that overlaps at least one of the first region and the second region.
Of the regions that overlap with at least one of the third region and the fourth region in one of the pair of first side walls when viewed from a direction perpendicular to one of the pair of first side walls. The area of the region pressed by the spacer is 20% or less of the area of one of the pair of first side walls that overlaps at least one of the third region and the fourth region.
When viewed from a direction perpendicular to one of the pair of first side walls, one of the pair of first side walls has the first boundary from the end of the positive electrode joint on the sealing plate side. From the region of 0.75 × L1 to L1 toward the portion and the bottom end side of the positive electrode joint, the second
The region overlapping the region of 0.75 × L3 to L3 toward the boundary portion was pressed by the spacer.
Batteries assembled.

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